The invention relates to an apparatus for distributing granular material.
The invention relates more particularly to an apparatus for delivering a granular explosion suppressant to the site of an explosion, an incipient explosion, or a deflagration.
There are many types of granular materials, used for many applications. In some applications, it is desirable to distribute the material in a particular pattern. The distribution pattern is sometimes referred to as the xe2x80x9cspreadxe2x80x9d of the granular material.
For example, some types of explosion suppressing systems operate by blowing granular suppressants into a location that is to be protected from explosion. Explosion suppressing systems are widely used in applications where potentially explosive substances such as dusts or vapors are present, especially when those explosive substances are sealed or otherwise enclosed within a limited volume. Examples of locations that might be protected include, but are not limited to, granaries, flour mills, food and pharmaceutical processing machines, petrochemical distillation equipment, solvent baths, etc.
In explosion suppressing systems it is often advantageous to produce a broad, relatively even distribution of suppressant material, without the necessity of moving the distribution device. Such a device is described herein as an exemplary embodiment according to the principles of the claimed invention.
However, it is noted that the claimed invention is not limited only to explosion suppression systems. Devices and methods according to the principles of the claimed invention may be suitable for a variety of other applications, as well. For example, when loading grain into silos or bins it is often advantageous to produce a broad and even spread of grain, rather than to produce a pile directly beneath the loading point.
With regard to terminology, it is noted that in the art of explosion suppression, the term xe2x80x9cexplosionxe2x80x9d is commonly used to refer particularly to the rupture of a vessel or other enclosure. Even if flames are present within a vessel, this is not considered an explosion unless the vessel fails physically, i.e. is breached, shattered, melted, etc. Cases where flames are present but the vessel has not exploded are commonly referred to as xe2x80x9cdeflagrationsxe2x80x9d, or alternatively as xe2x80x9cincipient explosionsxe2x80x9d. Explosion suppression typically focuses on extinguishing a deflagration before a vessel or enclosure actually explodes.
In addition, although the term xe2x80x9cgranularxe2x80x9d is sometimes used to refer to materials that are particularly coarse, it is not used in this narrow sense herein. With respect to the claimed invention, xe2x80x9cgranular materialxe2x80x9d includes any flowable material composed of individual solid bodies. Thus, it includes extremely fine material such as flour and other powders, extremely coarse material such as large gravel, and material of intermediate coarseness such as sugar.
With regard to the exemplary case of explosion suppressing systems, at least three major types are known. None are entirely satisfactory.
So-called fixed spreader systems comprise a spreader assembly that extends into the volume that is to be protected. An example of a fixed spreader system 10 is shown in FIG. 1. As may be seen therein, a pressurizer 12 is connected to a reservoir 14 for suppressant. The pressurizer 12 and reservoir 14 are connected to a flange 16 that is mounted to the wall 18 of the vessel that is to be protected. A spreader head 20 extends past the wall 18, and into the interior of the vessel.
When activated, the pressurizer 12 puts pressure on the suppressant in the reservoir 14, and forces it through the spreader head 20. The suppressant spreads out from the spreader head 20 into the vessel, and extinguishes the deflagration, thus preventing the explosion.
Fixed spreader systems suffer from a number of disadvantages.
First, the spreader head 20 protrudes into the protected volume. Many volumes that are or might advantageously be protected from explosions include working machinery, such as grinders or mixers. If a fixed spreader system is to be used for such applications, the machinery must be designed so as to avoid the spreader head, or there is a risk of damage to either the machinery or the head itself.
Second, the open structure of the spreader head 20 protruding into the vessel provides many places where contaminants and/or bacteria may accumulate. This is a particular drawback for applications that require a high degree of hygiene, such as food and pharmaceutical processes.
Even if the spreader head 20 is somehow covered, as by a spreader cap 22, the need to arrange machines to avoid it leaves a xe2x80x9cdead zonexe2x80x9d surrounding the spreader head 20. Contaminants and bacteria can build up in this area as well.
Another known explosion suppressing system is the so-called flush system, illustrated in FIG. 2. Like a fixed spreader system 10, a flush spreader system 30 comprises a pressurizer 32 connected to a reservoir 34. The pressurizer 32 and reservoir 34 are connected to a spreader assembly 36 that is mounted to the wall 38 of the vessel that is to be protected.
The spreader assembly 36 does not penetrate the vessel wall 38, and thus it avoids some of the disadvantages of the spreader head 20.
However, conventional flush spreader assemblies 36 are extremely complex, requiring many parts, some of which move during operation. As a result, they are very difficult and expensive to build and install.
Furthermore, after an explosion suppressing system activates, it must be serviced. This includes such tasks as recharging the pressurizer, adding more suppressant, etc. It is also necessary to clean the system, and replace any parts that were damaged or worn when the system activated. Since conventional explosion suppressing systems operate at pressures of up to 900 psi or more, damage is not uncommon, and certain parts are considered disposable.
Because the flush spreader assembly 36 is so complicated, even servicing and even routine maintenance can be time-consuming and complex.
In addition, the highly complex mechanisms in the spreader assembly 36 provide opportunities for the accumulation of contaminants and the growth of bacteria.
A third known explosion suppressing system is the telescopic system, shown in FIG. 3.
As with other conventional systems, a telescopic spreader system 50 includes a pressurizer and a reservoir (not shown in FIG. 3). The pressurizer and reservoir are connected to a spreader assembly 52. The spreader assembly 52 is mounted at least proximate to, and sometimes in contact with, a flange 54 that is mounted to the wall 56 of the vessel that is to be protected. The flange defines an aperture 58 therethrough.
The aperture 58 is covered by a burst seal 60, which is held in place by a clamp ring 62 and sealed with a gasket 64.
The spreader assembly 52 includes a spreader head 66 disposed inside of a housing 68. The spreader head 66 is movable with respect to the housing 68. When activated, the spreader head 66 is propelled forward (to the left, as illustrated) and partially out of the housing 68. The spreader head 66 punches through the burst seal 60, extending past the vessel wall 56 and into the protected vessel. Suppressant flows through the spreader head 66, extinguishing or preventing explosions.
A shock ring 70 around the spreader head 66 helps to absorb the impact of the spreader head 66, and also seals the spreader head 66 against the housing 68.
The telescopic spreader system 50 also avoids some of the disadvantages of the fixed spreader system 10. While not in use, it does not extend into the volume it protects. However, in the event of an explosion or an impending explosion, the spreader head 66 enters the vessel at high speed. Thus, there is the potential for damage to machinery inside the vessel and/or the spreader head 66. Alternatively, there is a loss of capacity and the potential for the build-up of contaminants and bacteria if the area the spreader head 66 occupies when in use is left unoccupied.
Furthermore, though less complicated than a conventional flush spreader system 30, the telescopic spreader system 50 is also an extremely complex device, with moving parts, that must deploy at high speed.
In addition to the drawbacks noted with respect to each of the three conventional types of explosion suppressing systems, conventional systems of all types generally require components made of rubber, such as gaskets, shock rings, seals, etc. This is disadvantageous for several reasons.
Rubber tends to degrade over time. Although certain types of rubber are more stable than others, given a sufficient duration most or all will crumble, become brittle, etc. In addition, exposure to certain chemicals, particularly solvents but also other flammable vapors and dusts that may be present in the protected volume, is known to degrade most types of rubber.
Since explosive events are typically rare, explosion suppressing systems may remain dormant and ready for months or years at a time. If rubber components have deteriorated during that time, the systems may not work as designed.
Furthermore, most types of rubber are at least slightly porous, and/or absorb water. As such, they provide a suitable medium for the growth of many types of bacteria. This is true even if the rubber is relatively well sealed and protected. Thus, the use of rubber in spreaders poses a problem of cleanliness and hygiene.
It is the purpose of the claimed invention to overcome these difficulties, thereby providing an improved apparatus and method for distributing granular material, and in particular for suppressing explosions.
An exemplary embodiment of an apparatus in accordance with the principles of the claimed invention includes a flange. The flange is disposed proximate the volume in which explosions are to be suppressed, and hence to which an explosion suppressant is to be distributed.
A burst seal is affixed to the flange.
A spreader insert is disposed proximate the flange, and may be in contact with it. The insert defines at least one aperture therethrough. The aperture or apertures generally form the shape of one or more annuli. That is, taken together, the apertures approximate rings in shape. It has been determined that such a configuration of apertures produces an unusually broad angular distribution of suppressant, herein referred to as the effective spread.
The insert is aligned with the flange such that the apertures are aligned with the seal.
The insert is adapted to be connected with a source of pressurized, granular suppressant. When pressurized suppressant is applied to the insert, it passes through the apertures, bursts the seal, and is directed into the protected volume by the insert.
In a preferred embodiment, the suppressant is distributed with an effective spread of at least 60 degrees. In a more preferred embodiment, the suppressant is distributed with an effective spread of at least 90 degrees. In an even more preferred embodiment, the suppressant is distributed with an effective spread of at least 100 degrees. In a still more preferred embodiment, the suppressant is distributed with an effective spread of at least 110 degrees. In a yet more preferred embodiment, the suppressant is distributed with an effective spread of at least 120 degrees.
In another preferred embodiment, the apparatus includes no rubber components.
In yet another preferred embodiment, the apparatus is made entirely of metal. In a more preferred embodiment, the apparatus is made entirely of stainless steel.
In a preferred embodiment, the apparatus has no functionally moving parts.
In still another preferred embodiment, the apparatus is adapted to be hygienically sealed.
In another preferred embodiment, each aperture defines a centerline thereof. The centerline of each aperture is at a uniform angle to the surface of the insert that is closest to the burst seal. In a more preferred embodiment, the angle of each aperture ranges between 30 and 65 degrees.
In an alternative embodiment, the insert may define apertures generally in the shape of two or more annuli. In a preferred embodiment, the multiple annuli are concentric.
In a preferred embodiment, the flange is adapted to be mounted flush to a surface, such as a vessel wall, so that it does not protrude into or past that surface, and into the volume that is to be protected when dormant, and such that only the burst seal protrudes past the wall and into the vessel when activated.